Coherence of transport variability along outer Banda Arcs

Abstract

Previous study hypothesized that the Pacific equatorial waves could enter into the interior Indonesian Seas and influenced the Indonesian Throughflow (ITF) along its eastern pathway. Here we investigate the variability of volume transport in the upper 500 m depth and its coherency along the outer Banda Arcs (OBA) channel from Ceram Sea (CS) to Aru Basin (AB) to western Timor Passage (TP) using daily INDESO model output (2008-2014). As expected, mean volume transport along OBA is in clock-wise direction: +1.04 (±1.54) Sv eastward in CS, -0.61 (±0.79) Sv southward in AB, and -8.42 (±2.05) Sv westward in TP, respectively. The vertical structure of currents is prominently intensified in the upper 300 m layer. Scales of transport variability in CS and AB are dominated by annual period with secondary in intraseasonal (ISV) period. In contrast, TP dominant periodicities are on the semiannual and ISV scales. Transport variability on ISV 30-43 days period among CS - AB - TP shows a significant coherence (>0.8) and phase difference (2-5 days) with signal in CS leading to AB and TP. This suggests a presence of Pacific equatorial waves which propagate along OBA channel.